Lifeboat Models

Model Lifeboats Built to Perform

Atlantic Motor Build the Outer Case

A Number of people have contacted me over the time of the building and developing of the outboard motors asking for more detail on how they are made.

On this page I will go through the making of each of the component parts of the build and how they go together.

The first part is the Gearbox case this starts life as flat aluminium bar 25mm x 12 mm a piece is then cut off and machined to 30mm long.

This is then marked out for the two holes that need to be bored it and tapped to a M10 thread. in the picture below you can see the two punch marks the one on the 30mm face is half way along and is for the horizontal shaft the other is on the 25mm face and is 11mm from the front of the box.

The holes in the box will end up like this with the red area threaded and the smaller part of the horizontal hole being for a oil-lite bearing 6mm OD

Here is the block in a 4 jaw chuck with the horizontal hole bored and threaded. The first part is to use a centre in the tailstock to help locate the block in the chuck this is done by aligning the punch mark with the point.

Once the job has been centred a 5mm hole is drilled to the full depth of the bearing this is then drilled out to 8mm to the depth of the main shaft. The bearing hole is then enlarged to 5.8mm to make the bearing a push fit.

Once this is done the main hole is enlarged to 8.5mm and the bottom flattened of with the small boring tool that can be seen in the picture. The hole is then taped out with an M10 tap.


When this is completed the block is rotated and the hole for the vertical shaft is drilled and taped.


The next component is the vertical shaft outer case. This is a piece of round bar 70mm long with a 5mm hole up the middle and a bearing in one end. The outside is machined down to 8mm apart from the ends which are 10mm and threaded.

The first task is to drill a 5mm hole up the middle of the bar. This needs a long bit as a standard 5mm bit is too short.


The end is then enlarged to 5.8mm and a bearing pushed in with the tailstock chuck.


The bar is then machined down to 10mm and then 8mm apart from the ends.


The two ends are then threaded and the finished part cut off to length.


Here are two gearbox cases and vertical outer case fitted.


The last part of the outer casings is the plug that holds the horizontal shaft in place. This is made by turning a bar down to 10mm and the threading it a 3mm hole is drilled up the middle and then a hole is drilled to take the bearing and a bearing pushed in just like the vertical shaft. A small shoulder is then turned on this before it is parted off.

Once the piece is removed from the lathe two flats are cut on the shoulder to allow a spanner to turn the plug as it is fitted into the main casing.

The last thing to do with the main case is to fit the bearing in to take the inside end of the horizontal shaft this is done by a tapping it in with a small brass bar.